@bc:#010309;
.nav {
    display: flex;
    height: 50px;
    width: 50vw;
    line-height: 50px;
    background-color:@bc;
    .nav-item {
        flex: 1;
        color: #fff;
        text-align: center;
    }
}
#app {
    display: flex;
    height: 50px;
    width: 50vw;
    line-height: 50px;
    background-color:@bc;
.nav-item {
    flex: 1;
    color: #fff;
    text-align: center;
    }
}